[Libreoffice] Objective C in slideshow

[Norbert Thiebaud]

OGLTrans in slideshow on Mac as a couple of Objective/C (by opposition
ot Objective/C++) files.

Unfortunately gbuild did not have support for .m files (and silently
did nothing for things like
$(eval $(call gb_Library_add_objcobjects,OGLTrans,\
    slideshow/source/engine/OGLTrans/mac/aquaOpenGLView \
    slideshow/source/engine/OGLTrans/mac/OGLTrans_Shaders \
    , $(gb_LinkTarget_EXCEPTIONFLAGS) \
))

or in general if a method dos not exist, it apparently silently does nothing.
the result was that the link was failing due to the lack of the
objects associated with these .m files

I added support for Objective/C in gbuild:
see bootstrap:4e8371c559d9cf677a1bc7e6a34161c5df4e2365
http://cgit.freedesktop.org/libreoffice/bootstrap/commit/?id=4e8371c559d9cf677a1bc7e6a34161c5df4e2365

Bjoern, I'd appreciated If you could give it your blessing... (or do
your usual 'small changes' ;-) )

Norbert